Field of the Invention
This invention relates generally to a machine for exercising the rotator cuff muscles and, more particularly, to a machine that separately exercises each of the rotator cuff muscles by effectively isolating each muscle while the user is in a seated position.
Discussion of the Related Art
The human shoulder includes three bones, namely, the clavicle, the scapula and the humerus, which are held together in a specific spatial relationship by muscles, tendons and ligaments. The clavicle attaches the shoulder to the sternum and connects to the scapula at a bony projection, known as the acromion, that extends from the scapula along the top of the shoulder. The shoulder joint, known as the glenoid fossa, is formed where a ball at the top of the humerus fits into the scapula in a ball and socket joint, which is one of the largest and most complex joints in the human body.
A number of muscles stabilize the shoulder and allow for its proper motion. These muscles include a group of four rotator cuff muscles, namely, the supraspinatus, the infraspinatus, the teres minor, and the subscapularis. Each muscle of the rotator cuff muscle group originates on the scapula and includes a tendon that inserts on the humerus. The supraspinatus, infraspinatus and teres minor muscles originate on the posterior surface of the scapula and insert on the humeral head superiorly and posteriorly. The subscapularis muscle originates on the anterior surface of the scapula and passes in front of the humeral head to attach medially to the humeral neck. The supraspinatus muscle abducts the humerus away from the body at a 30° angle. The infraspinatus muscle abducts and externally rotates the humerus when the elbow is held at the side, immediately adjacent to the torso. The teres minor muscle externally rotates the humerus when the shoulder is abducted at 90° to the side. The subscapularis muscle internally rotates the humerus when the arm is at the side.
Together, the rotator cuff muscles provide for proper positioning of the humeral head in the glenoid socket while the shoulder is at rest by creating an inferior and medial force vector. The rotator cuff muscles also provide dynamic stability to the shoulder joint by creating a force vector that maintains proper positioning of the humeral head within the glenoid socket during active elevation of the shoulder, particularly in the first phase of the arc of motion.
The deltoid muscle is a large muscle that originates medially on the scapula along the acromion and a portion of the clavicle. The deltoid crosses the shoulder and attaches to the humerus, and functions to elevate and abduct the humerus away from the torso. The pectoralis muscle is a large muscle in the chest that inserts into the humerus and is responsible for flexing, internally rotating and adducting the humerus. Together the deltoid and pectoralis muscles pull upward and anteriorly, opposing the action of the rotator cuff muscles, which pull inferior and medially.
There exists a dynamic balance between the rotator cuff muscle group and the deltoid/pectoralis muscle group. When a healthy balance exists, there is a force coupling generated by these opposing muscle groups to allow for proper elevation of the humerus from a position where the arm is at the side to a position above the head. Without a healthy and sufficiently strong rotator cuff muscle to keep the humeral head seated properly in the glenoid, the humeral head would simply slide up the glenoid due to the unopposed action of the deltoid and pectoralis muscles until it makes contact with the acromion and is extruded out the front of the shoulder. At that point further elevation, past 30° or so, would not be possible.
The natural aging process results in a much greater decrease in rotator cuff muscle strength than in deltoid and pectoralis muscle strength. This naturally increasing imbalance results in impingement of the rotator cuff tendons as they are pinched between the humeral head and the acromion. As a person ages and/or the rotator cuff muscles are weakened, the ball of the humerus typically rides higher in the socket than desired, which acts to abrade the tendons of the rotator cuff muscles, known as rotator cuff impingement. By strengthening the rotator cuff muscles, the ball will maintain a lower, more mechanically efficient, position in the socket during elevation, thereby reducing impingement.
Rotator cuff muscle imbalances are common in sports as well. Many athletes, such as baseball players and swimmers, often wish to strengthen the rotator cuff muscles as part of their athletic training to offset over developed deltoid and pectoralis muscles. This can increase their performance and prevent rotator cuff impingement.
As with any muscle and tendon, the rotator cuff muscles are susceptible to injury, such as tears, strains, tendonitis, inflammation, bursitis, etc., as a result of damage or overuse all typically resulting in pain. The supraspinatus muscle is especially susceptible to injury and is the most commonly injured muscle of the rotator cuff muscle group.
Most diagnosed rotator cuff injuries and conditions are typically non-operative and require rehabilitation that specifically targets the rotator cuff muscles through exercise and strength training to improve the dynamic balance of the shoulder. Physicians who treat rotator cuff muscle injuries often send their patients to rehabilitation to perform rotator cuff muscle strength training and exercises under the guidance of a physical therapist. During physical therapy of the rotator cuff muscles, each of the four rotator cuff muscles needs to be separately isolated so that it fires independently of other muscles, rotator cuff or otherwise, in order for that muscle to be properly strengthened. To do this, the physical therapist will typically use resistance devices, such as bands and free weights, while the patient's arm is maintained in a specific orientation for each muscle exercised. Maintaining the patient's arm in the proper orientation is crucial to prevent other muscles not being targeted from firing during the exercise.
Once the physical therapy has ended, the patient is now on his or her own to perform the exercises without the guidance of the physical therapist. However, without the specific guidance of a therapist, it is typically very difficult for the patient to consistently replicate the exercise with proper form so that only the specific muscle being targeted is actually exercised.
Furthermore, piecemeal equipment set up, utilized at home, is cumbersome and to use it correctly requires consistent, meticulous attention to detail. For these reasons, compliance with a permanent home exercise program is notoriously poor, and in the vast majority of cases, nonexistent. This results in frequent relapses of pain and dysfunction as a result of the “honeymoon effect” of their formal physical therapy wearing off. The rotator cuff muscles once again become deconditioned and the dynamic imbalance between the rotator cuff muscles and deltoid/pectoralis muscles resumes, with the subsequent return of the impingement and symptoms.
Machines for exercising the rotator cuff muscles exist in the art for exercising the rotator cuff muscles of a user. These machines are typically pulley based, where the user moves a cable against some resistance. However, these machines are typically not suitable for isolating and targeting the individual rotator cuff muscles because they do not include any mechanisms for ensuring that the orientation of the user's arm is maintained in a correct position, thus preventing isolation of the specific, targeted rotator cuff muscle. Without ensuring isolation, the shoulder will recruit the surrounding muscles, most notably the deltoid and pectoralis muscles, further contributing to the muscle imbalance, rather than helping to correct it.
Currently, no exercise machine exists that is able to separately isolate each of the rotator cuff muscles individually, while simultaneously and specifically preventing the exercise from being performed if the user's arm is not oriented properly for the particular muscle.
Because rotator cuff muscle exercises and the existing available exercising apparatus makes it difficult to specifically isolate the rotator cuff muscles, performing shoulder exercises in an attempt to strengthen these muscles oftentimes, as mentioned above, has the opposite effect. Because the stronger deltoid and pectoralis muscles are easily and unintentionally recruited in rotator cuff exercises, the strength differential between the deltoid/pectoralis muscles and the rotator cuff muscles is further exaggerated, to the detriment of the rotator cuff muscles. Therefore, unless the rotator cuff muscles are exercised with the arm in a specific orientation, the exercise may do more harm than good. Hence, it is critical that a rotator cuff muscle exercise be performed properly, where the orientation of the user's arm is correct, depending on which specific muscle is being exercised, in order to prevent the deltoid and pectoral muscles from being unintentionally and simultaneously strengthened during the rotator cuff muscle exercise.